Viewers of President Obama's State of the Union address will have noticed that as he arrived in the House chamber he was accompanied by a delegation of congressional leaders, notably the House majority leader and the president pro tempore of the Senate. The former is Rep. Eric Cantor of Virginia. The latter is Sen. Patrick Leahy.

Leahy's longevity in the Senate has earned him status as the most senior member of the majority party, which elevates him to the position of president pro tempore. The Constitution provides that Vice President Joe Biden is the president of the Senate; in the absence of the vice president, the presiding officer is the president pro tempore, which is Latin for “for the time being.”

President pro tempore is largely a ceremonial position, occupied usually by senators of advanced age. Some of the senators who occupied the position in recent decades have included Robert Byrd, Ted Stevens and Strom Thurmond. Leahy became the most senior senator upon the death of Daniel Inouye of Hawaii.

Leahy has taken up the post at a relatively young age, 72, because he was elected to the Senate in 1974 at a young age, 34. He has expressed delight at his status as the Senate's most senior member, and he seemed to be enjoying his role as escort for the president to and from the House last week.

Leahy's senior status is likely to have more telling effect in ways apart from his role as pro tem. As chairman of the Senate Judiciary Committee he is squarely in the thick of some of the most contentious and consequential issues of the day. These include bills on gun control, immigration and domestic violence.

On other committees, the Democrats who preside as chairmen are not necessarily the kind of dependable ally that Obama might prefer. Sen. Max Baucus, the Montanan who is chairman of the Senate Finance Committee, was a major headache for the president during the drafting of the Affordable Care Act. Leahy, on the other hand, has been a consistent supporter of the president and appears ready to put all his weight behind the critical measures that Obama is promoting.

After Obama's decisive re-election in November a political shift has altered the prospects for legislation in Washington. The news has been dominated by the continuing gridlock created by the budgetary blackmail practiced by Republicans. But in other areas gridlock is easing.

Thus, the times are catching up with Leahy. Republicans who competed last year to determine who could be most mean-spirited toward immigrants now acknowledge that some sort of path toward citizenship for undocumented foreigners will be necessary. Leahy is in a position to help craft and push toward passage the kind of immigration reforms sought by Obama and acceded to by Republicans in the aftermath of their election debacle.

On gun control Leahy stepped forward soon after the slaughter in Newtown, Conn., to announce that he would hold hearings on gun violence. He has let it be known that he will push for an array of measures for which popular support is widespread, including universal background checks.

Leahy's position has already yielded results. Earlier this week the Senate passed the Violence Against Women Reauthorization Act, which renews a bill that Congress allowed to lapse two years ago. It is an important law assisting victims of domestic violence and sexual violence and includes provisions targeting the trafficking of women.

That Congress was willing to allow this measure to lapse two years ago says something about the priorities of the do-nothing Congress that completed its term last year. That the Senate has been willing to take bipartisan action early in the new session to protect women against violence says something about the new political atmosphere in Washington.

Leahy's leadership is likely to flower in this new atmosphere. His ceremonial duties as president pro tempore are gilding on the lily.